Wind-powered turbine ventilators are widely used for under-roof ventilation in domestic, commercial and industrial applications. Their popularity stems largely from a relatively modest purchase cost coupled with a substantial absence of any operating cost and ability to operate passively without regulation. The primary purpose of the turbine ventilator is to exhaust under-roof accumulation of hot air either internally generated or as a result of sun loading on the roof. For that purpose, a precise quantity of air flow need not be maintained continuously but can instead be permitted to fluctuate within a wide range.
Being wind powered, capacity fulfillment of the turbine ventilator to induce a forced air flow upward through a roof opening is dependent upon and will fluctuate extensively in correlation to ambient wind velocity. Continuous exposure to varying wind and rotational forces subjects the ventilator and its bearing supports to severe vibration and wear.
Conventional wind powered turbine ventilators are available in various sizes affording a rated flow capacity at a given wind velocity. Their construction usually includes a vaned head mounted for rotation relative to a stationary mounting bracket. The mounting bracket is configured for attachment onto a roof-mounted air flow conduit such as an adjustable sheet metal elbow fitting which is centered over a circular cut-out opening in direct communication with the space to be ventilated. In conventional turbine design, exterior bracing may be provided to aid in securing the turbine components relative to each other while an axially depending internal spindle in cooperation with a stationary sleeve provides a journalled support for rotation.
Conventional turbines include a stationary spindle, usually a metal rod or tube, that extends from a mounting bracket (located below the turbine base) up to the top of the turbine, or to the upper region of the turbine. The spindle is positioned vertically at the center of the turbine, often measuring approximately 10 inches in length, and the turbine rotates around it. The weight of the rotating turbine member is borne solely by the spindle. The turbine engages the spindle by a thrust bearing tip at the upper end of the spindle, and may include plastic bushings and ball bearings, all of which stabilize the turbine on its axis so that the turbine will spin freely in the wind.
Conventional turbine ventilators are disclosed in U.S. Pat. Nos. 3,392,659 and 3,590,720. Specific support structures for a variety of interlocking turbine components are disclosed in U.S. Pat. Nos. 3,179,367; 4,441,347 and 4,653,708.
Because of the rapidly rising costs of energy, the incentives to conserve energy are increasing, both for domestic users as well as industrial users. For most domestic users in the southern regions of the United States, home air conditioning accounts for a substantial portion of the annual energy expense. Although most dwellings are insulated, a substantial amount of energy is expended by the air conditioning compressor to pump the radiant heat absorbed by the dwelling structure out of the air conditioned living space and into the outside ambient air.
The air conditioning load is intensified by the thermal storage effect associated with the attic air space found in most dwellings. Air circulates very slowly in the attic air space so that its temperature rises rapidly as solar radiation is absorbed. As a result, a large amount of heat is transferred from the exposed roof structure to the air trapped within the attic air space. The body of air trapped in the attic space acts as a thermal reservoir which transfers heat through the ceiling and into the conditioned living space. Because of the large thermal mass associated with the attic air space and the roof structure, heat transfer through the ceiling and into the conditioned living space may continue for several hours after sundown.
The thermal oven effect of the trapped attic air may be reduced by the action of vents, roof turbines and attic ventilator fans which circulate the trapped air out of the attic space.
Traditionally, roof-mounted turbine ventilators are made of metal construction: steel or aluminum. Plastic bushings and/or ball bearing assemblies are commonly used to provide smooth rotating action. Turbine ventilators have been made this way for over 60 years with the only major innovation being the introduction of some units using ball bearings and plastic bushings, and some units using aluminum vane components instead of galvanized steel. Conventional metal turbines basically consist of an upper crown, riveted individual vane members, and a lower base with radial members that extend inward to support the lower region of the turbine and provide a housing for the lower bushing or ball bearing that engages, the spindle. Conventional turbines typically include 20 to 24 convex-shaped metal vane members, 8-inches in length extending from top to bottom of the turbine. In all of these commercially available turbines, the steel or aluminum vanes are individual, separate component members. Each vane has a rivet hole punched at the top of the vane and at the bottom of the vane for assembly purposes.
During the turbine manufacturing process, as many as twenty to twenty-four individual vanes are attached by rivet to a crown plate and a base collar. Handling each individual vane and riveting of each vane twice requires forty to fifty rivet fasteners and an equal number of rivet setting operations per turbine assembly. The curvature of these vanes is such that they bow out in a convex profile, with the assembled turbine having a globe-shaped silhouette.
With the current trend to form these vanes from thinner sheet metal stock to reduce the turbine weight, these globe-shaped products are easily dented. These light-weight turbines often take an impact while shipping in their corrugated container, or from a flying bird while affixed to the roof of a home resulting in a permanent and noticeable dent. Once this happens, the turbine will not spin true as it should. A dented turbine head will display a noticeable wobble as it rotates, lose some of its ventilating effectiveness and give the appearance of a flawed product. This conventional metal turbine design requires many separate assembly operations during its manufacture, and the finished product is very labor intensive.
The turbine head of the present invention includes an upper head assembly and a lower head assembly, with vane segments being integrally formed on the upper head assembly, and complementary vane segments being integrally formed on the lower head assembly. The lower head assembly and upper head assembly are separately molded, and are assembled together with the complementary vane segments being fitted together to complete the turbine head. A separate air scoop assembly including air scoop blades are attached to the turbine for drawing hot air from the attic space in response to turbine rotation due to wind action, and for inducing a turning moment in the turbine in response to the convection flow of hot air that rises from the attic space when ambient wind conditions are not sufficient to turn the turbine head.
Vertical section panels mounted within the turbine interior partition the rising exhaust air to evenly and uniformly distribute the exhaust air through exhaust ports located in vertical slots between adjacent vane members. An internal exhaust air diffuser cone directs exhaust air through the turbine to cause it to move in close proximity through a venturi passage, thus accelerating the flow of exhaust air and promoting the removal of exhaust air from the attic space. In the preferred embodiment, each turbine vane includes three segments, with two segments forming a pocket for capturing the incident ambient wind currents on one side of the turbine, while adjacent vane segments form a venturi passage for promoting the withdrawal of air through the opposite side of the turbine. A separate cover is removably attached to the crown portion of the turbine and provides a weather seal for the upper spindle and bearing assembly.